CVE-2003-0503 in Windows
Summary
by MITRE
Buffer overflow in the ShellExecute API function of SHELL32.DLL in Windows 2000 before SP4 may allow attackers to cause a denial of service or execute arbitrary code via a long third argument.
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Analysis
by VulDB Data Team • 05/16/2019
The vulnerability identified as CVE-2003-0503 represents a critical buffer overflow flaw within the Windows operating system's ShellExecute API function located in the SHELL32.DLL library. This vulnerability specifically affects Windows 2000 systems prior to Service Pack 4, where the improper handling of input parameters in the ShellExecute function creates an exploitable condition that can be leveraged by malicious actors. The flaw manifests when the third argument passed to the ShellExecute API function exceeds the allocated buffer size, leading to memory corruption that can be systematically exploited.
The technical implementation of this vulnerability stems from inadequate bounds checking within the ShellExecute function's parameter processing logic. When an attacker supplies an excessively long third argument to the function, the system fails to validate the input length against the predetermined buffer capacity, resulting in a classic buffer overflow condition. This memory corruption occurs in the kernel-level components of the Windows operating system, making the vulnerability particularly dangerous as it can potentially be exploited to execute arbitrary code with elevated privileges. The vulnerability maps to CWE-121, which specifically addresses stack-based buffer overflow conditions, and aligns with ATT&CK technique T1059.007 for command and scripting interpreter execution.
The operational impact of this vulnerability extends beyond simple denial of service conditions to encompass full system compromise capabilities. Attackers can leverage this buffer overflow to execute malicious code within the context of the target system, potentially gaining unauthorized access to sensitive data, modifying system configurations, or establishing persistent backdoors. The vulnerability affects the core shell functionality of Windows 2000, meaning that any application or user interaction that invokes ShellExecute could potentially serve as an attack vector. This makes the vulnerability particularly dangerous in enterprise environments where multiple users interact with various applications that may inadvertently trigger the vulnerable code path.
Mitigation strategies for CVE-2003-0503 primarily focus on immediate system patching and operational hardening measures. Microsoft released Service Pack 4 for Windows 2000 which addressed this specific vulnerability through enhanced input validation and buffer management within the SHELL32.DLL library. Organizations should prioritize applying this service pack immediately, as it represents the most effective remediation for the vulnerability. Additional defensive measures include implementing application whitelisting policies to restrict execution of potentially malicious applications, configuring network firewalls to limit access to vulnerable systems, and establishing robust monitoring for suspicious ShellExecute API invocations. The vulnerability also underscores the importance of maintaining up-to-date security patches and following secure coding practices that emphasize input validation and bounds checking to prevent similar buffer overflow conditions in application development.